A primary reason for malpractice suits against radiologists is missed cancer. Such suits are often based on missed breast cancer on mammography and missed lung cancer on chest x-rays. To a smaller degree, errors on CT scans have also led to legal actions. Currently, there is no objective standard for measuring the effectiveness of human observers and/or computer controlled visioning equipment for finding cancer lesions. Missed cancers are often reviewed using hindsight and knowledge of facts not available to the original observer. As a result, such reviews often produce diametrically opposed opinions regarding whether an incidence of missed cancer fell below a standard of care.
In a typical scenario, a patient has undergone an imaging procedure producing a medical image. Although present in the medical image, a lesion is missed and not identified by a reader, such as a radiologist. Subsequently, cancer is discovered when the patient either has the imaging done again or has become symptomatic. A malpractice claim may result where it is typically alleged that the radiologist should have seen the lesion on the original study. It may be further alleged that, because the lesion was missed, it has progressed making the lesion less amenable to treatment and thereby increasing the risk of death.
One of the most challenging aspects of such malpractice cases turns on whether the missed abnormality was readily identifiable on the initial examination according to accepted medical practice. Unfortunately, criteria for determining the visibility of a cancerous abnormality are quite vague. A lesion may have low conspicuity on an early scan image. However, once a lesion is known to exist in a specific location, an informed observer may opine that the lesion is fairly obvious on a medical image. Using such hindsight, a fact-finding body, such as a jury, may make a determination of malpractice in questionable circumstances. As a general rule, when an expert participates in a case, the expert reviews the images and determines whether a particular lesion should have been missed or found. Often the expert reviews a series of images taken over time and determines the point at which the lesion should have been visible. Ultimately, there are no objective standards for determining the visibility of lesions on medical images.
A visibility index for medical imaging has heretofore been lacking. As a result no objective standard for measuring the effectiveness of the interpretation of a medical image, whether by human or automated system, has been made available.